Axial flux stator and method of manufacture thereof

ABSTRACT

An axial flux stator includes a plurality of magnetically permeable members, a plurality of windings, a back iron, and an encasing. The plurality of windings is associated with the plurality of magnetically permeable members to produce a plurality of winding-magnetically permeable member assemblies. The back iron is mechanically butt joint coupled to the plurality of winding-magnetically permeable member assemblies. The encasing maintains the butt joint coupling of the back iron to the plurality of winding-magnetically permeable member assemblies.

CROSS REFERENCE TO RELATED PATENTS

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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

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BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention relates generally to electric motors and moreparticularly to stators.

2. Description of Related Art

As is known, there are various types of electric motors and an almostendless variety of uses for them. For instances, an electric motor maybe an AC motor (e.g., synchronous or induction), a servo motor, a DCmotor, or an electrostatic motor (e.g., magnetic motor) and may be usedin applications that range from micro-mechanical systems (MEMS), to foodprocessing equipment, to household appliances, to power tools, toautomobiles, to toys, to large manufacturing equipment, etc. Basicallyany device that uses mechanical motion includes an electric motor.

Due to the vast uses of electric motors, they come in an almost endlessvariety of sizes, shapes, and power levels. For instance, the size of aMEMS motor is small enough to fit on an integrated circuit and suppliesnano-watts of power, while a large manufacturing equipment motor may betens of feet in diameter supplying hundreds of thousands of kilowatts ofpower. Note that power of electric motors is sometimes expressed inhorsepower, where one horsepower equals 746 watts.

Regardless of the type, size, shape, and power level, an electric motorincludes a stator and a rotor. The stator includes coils that produce amagnetic field, which causes motion of the rotor (e.g., its output shaftrotates). For radial flux motors, the stator produces a radial flux(e.g., spreading out from the center); while stators of axial fluxmotors typically produce an axial flux (e.g., located along the plane ofthe axis).

While a motor contains two primary components (e.g., the stator and therotor), the manufacturing of a motor is far from a simple process. Forinstance, manufacturing a DC brushless pancake motor (e.g., a motorwhose width is greater than its axial length) requires the developmentof tooling to produce the components of the motor and/or to assemble thecomponents of the motor. Further, the manufacturing steps of producingthe motor can be quite expensive. For instance, a back iron of thestator is fabricated to include mechanical fittings to hold the statorpoles in place, which requires special tooling to produce. Then, inmanufacturing, the stator poles are physically pressed into themechanically fittings, which must be done in an identical manner toprevent variations in the mechanically coupling.

For certain applications (e.g., less than 10 horsepower), the cost oftooling and manufacturing has severely limited the production ofeconomical pancake brushless DC (BLDC) motors. Therefore, a need existsfor a stator and method of manufacture thereof to produce pancake DCmotors and other axial flux motors.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a cross-sectional side view diagram of an embodiment of anaxial flux stator in accordance with the present invention;

FIG. 2 is a three-dimensional perspective diagram of an embodiment of anaxial flux stator in accordance with the present invention;

FIG. 3 is a top view diagram of an embodiment of an axial flux stator inaccordance with the present invention;

FIGS. 4-8 are diagrams illustrating an example of manufacturing an axialflux stator in accordance with the present invention;

FIG. 9 is a cross-sectional side view diagram of an alternate example ofencasing an axial flux stator in accordance with the present invention;

FIG. 10 is a cross-sectional side view diagram of another embodiment ofan axial flux stator in accordance with the present invention; and

FIGS. 11-13 are diagrams illustrating another example of manufacturingan axial flux stator in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a cross-sectional side view diagram of an embodiment of anaxial flux stator 10 that includes a plurality of magnetically permeablemembers 12-14, a plurality of windings 16-18, a back iron 20, and anencasing 24. A magnetically permeable member 12-14 may be one or more ofa soft magnetic composite (SMC) stator tooth, a lamination steel stackstator tooth, a formed ferrite material stator tooth, and a steel sheetcoil stator tooth. The geometric shape of a magnetically permeablemember 12-14 may be a cube, a cylinder, a rectangular cube, arectangular cube with a top plate 15 (which is illustrated in thepresent figure), and/or any other shape to provide a stator tooth.

As is shown, the plurality of windings 16-18 are associated with theplurality of magnetically permeable members 12-14 to produce a pluralityof winding-magnetically permeable member assemblies or inductanceassemblies. For example, a winding 16-18 may include a bobbing thatsupports a wire coil, wherein the bobbin and the coil of wire are fittedaround a corresponding one of the magnetically permeable members 12-14.In another example, the winding 16-18 may be a coil of bondable wirethat is fitted around a corresponding one of the magnetically permeablemembers 12-14.

The back iron 20 may be one or more of a coil of steel ribbon, aplurality of laminated steel sheets, a soft magnetic composite, and aformed ferrite material. In this embodiment, the back iron 20 ismechanically butt joint coupled 22 to the plurality ofwinding-magnetically permeable member assemblies. As such, the back iron20 does not include mechanical fittings to couple with the magneticallypermeable members. In contrast, the magnetically permeable members 12-14“sit” on the back iron 20, which reduces the cost of tooling and ofmanufacturing an axial flux stator.

The encasing 24 may be one or more of an injection molding, anonmagnetic potting material, a nonmagnetic casting material, and apre-fabricated housing. For example, the injection molding may be athermally conductive plastic. The encasing 24 provides holds the backiron 20 and the plurality of winding-magnetically permeable memberassemblies together to maintain the butt joint coupling 22 of the backiron 20 to the plurality of winding-magnetically permeable memberassemblies.

FIG. 2 is a three-dimensional perspective diagram of an embodiment of anaxial flux stator 10 that includes the winding-magnetically permeablemember assemblies 26, a planar annular ring back iron 28, and theencasing 24. In this embodiment, the encasing 24 has a geometric shapecorresponding to the planar annular ring back iron 28 such that a rotormay at least partial reside within the opening in the center of theencasing 24.

FIG. 3 is a top view diagram of an embodiment of an axial flux stator 10that includes the plurality of magnetically permeable memory and windingassemblies 26 (e.g., 12 assemblies) and the encasing 24. In thisembodiment, the encasing is an injection mold thermally conductiveplastic 30. As is shown, the encasing includes an opening that providesa bearing and shaft area 32.

FIGS. 4-8 are diagrams illustrating an example of manufacturing an axialflux stator 10. In FIG. 10, the method of manufacturing begins byplacing a plurality of magnetically permeable members 12-14 within acarrying platform 40. The carrying platform 40 may be a pre-formedcomposite that includes a plurality of receptacles. Each of thereceptacles receives one of the magnetically permeable members 12-14 androughly holds it in a desired position. Such a carrying platform is ofmodest expense to produce.

FIG. 5 illustrates a side cross-sectional view of aligning the pluralityof magnetically permeable members 12-14 via an alignment plate 42. Inthis step, the alignment plate 42 adjusts the rough position of themagnetically permeable members 12-14 as established by the carryingplatform 40 to a more precise position in three-dimensional space toproduce a plurality of aligned magnetically permeable members. Thealignment plate 42 may be a die cut plate of various materials,including 10 mil Mylar sheet.

FIG. 6 is a three-dimensional perspective diagram of placing a pluralityof windings 16-18 on the plurality of aligned magnetically permeablemembers 12-14 to produce a plurality of winding-magnetically permeablemember assemblies 26. While not specifically shown, the alignment plate42 maintains the positioning of the magnetically permeable members 12-14and may provide a reference point for positioning the windings 16-18 onthe members 12-14. Note that an adhesive may be used to hold the members12-14 to the alignment plate 42 and to hold the windings 16-18 to thealignment plate 42 at the desired positioning with respect to themembers 12-14.

FIG. 7 is a side cross-sectional view of positioning a back iron 20 withrespect to the plurality of winding-magnetically permeable memberassemblies 26 such that a first primary plane of the back iron creates aplurality of butt joints 22 with the plurality of aligned magneticallypermeable members. The butt joints 22 provide the electro-magneticcoupling of the magnetically permeable members 12-14 with the back iron20. Note that the back iron 20 may be a coil of steel ribbon, aplurality of laminated steel sheets, a soft magnetic composite, and aformed ferrite material and may have a geometric shape of a planarannular ring.

FIG. 8 is a side cross-sectional view of encasing 24 the plurality ofwinding-magnetically permeable member assemblies 26 and the back iron 20to maintain the plurality of the butt joints 22. The encasing 24 may bedone with an injection-molded plastic, a nonmagnetic casting material,and/or with a nonmagnetic potting material. With such a method ofmanufacture, tooling costs and manufacturing costs are of a modestexpense, making it economically feasible to produce axial flux statorsfor use in various economical pancake DC motors and/or other axial fluxmotors.

FIG. 9 is a cross-sectional side view diagram of an alternate example ofencasing an axial flux stator 10. In this embodiment, the encasing isdone via a pre-fabricated housing 44. The pre-fabricated housing 44 maybe composed of an injection-molded plastic, a nonmagnetic pottingmaterial, and/or a nonmagnetic casting material. The housing 44 may havetwo pieces that are mechanically couple them together.

FIG. 10 is a cross-sectional side view diagram of another embodiment ofan axial flux stator 10 where the alignment plate 42 is replaced with aprinted circuit board (PCB) 40-1. In an embodiment, the PCB platform40-1 may have a plurality of traces for coupling to the plurality ofwindings. In another embodiment or in furtherance of the precedingembodiment, the PCB platform 40-1 may include a plurality of PCBwindings coupled to the plurality of windings.

FIGS. 11-13 are diagrams illustrating another example of manufacturingan axial flux stator 10. FIG. 11 is a three-dimensional perspective viewdiagram of assembling a plurality of inductance structures 50 to producea plurality of stator poles. An inductance structure 50 includes awinding wrapped around a magnetically permeable member. The magneticallypermeable member may be one or more of a soft magnetic composite statortooth, a lamination steel stack stator tooth, a formed ferrite materialstator tooth, and a steel sheet coil stator tooth. The winding may be abobbin supporting a wire coil and/or a coil of bondable wire.

FIG. 12 is a three-dimensional perspective view diagram of positioning anon-permeated planar back iron 52 with respect to the plurality ofinductance structures 50 to create a substantially air-gapless magneticcoupling between the non-permeated planar back iron and the plurality ofinductance structures. The non-permeate planar back iron 52 does notinclude mechanical fittings to couple with the magnetic permeablemembers of the inductance assembles 50 and may have a planar annularring shape. Further, the non-permeable planar back iron 52 may be one ormore of a coil of steel ribbon, a plurality of laminated steel sheets, asoft magnetic composite, and a formed ferrite material.

FIG. 13 is a three-dimensional perspective view diagram of encasing theplurality of inductance structures 50 and the non-permeated planar backiron 52 to maintain the substantially air-gapless magnetic coupling. Theencasing may be one or more of injection molding the plurality ofinductance structures and the non-permeated planar back iron, potting,with a nonmagnetic potting material, the plurality of inductancestructures and the non-permeated planar back iron, casting, with anonmagnetic casting material, the plurality of inductance structures andthe non-permeated planar back iron, and assembly the plurality ofinductance structures and the non-permeated planar back iron within apre-fabricated housing.

With such a method of manufacture as described in FIGS. 11-13 an axialflux stator having a plurality of inductance structures, a non-permeatedplanar back iron, and an encasing is economically produced. In anembodiment, an inductance structure includes a winding wrapped around amagnetically permeable member, which is substantially air-gaplessmagnetic coupled to the non-permeated planar back iron. The encasingmaintains the substantially air-gapless magnetic coupling between theplurality of inductance structures and the non-permeated planar backiron.

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “operably coupled to”, “coupled to”, and/or “coupling” includesdirect coupling between items and/or indirect coupling between items viaan intervening item (e.g., an item includes, but is not limited to, acomponent, an element, a circuit, and/or a module) where, for indirectcoupling, the intervening item does not modify the information of asignal but may adjust its current level, voltage level, and/or powerlevel. As may further be used herein, inferred coupling (i.e., where oneelement is coupled to another element by inference) includes direct andindirect coupling between two items in the same manner as “coupled to”.As may even further be used herein, the term “operable to” or “operablycoupled to” indicates that an item includes one or more of powerconnections, input(s), output(s), etc., to perform, when activated, oneor more its corresponding functions and may further include inferredcoupling to one or more other items. As may still further be usedherein, the term “associated with”, includes direct and/or indirectcoupling of separate items and/or one item being embedded within anotheritem. As may be used herein, the term “compares favorably”, indicatesthat a comparison between two or more items, signals, etc., provides adesired relationship. For example, when the desired relationship is thatsignal 1 has a greater magnitude than signal 2, a favorable comparisonmay be achieved when the magnitude of signal 1 is greater than that ofsignal 2 or when the magnitude of signal 2 is less than that of signal1.

The present invention has also been described above with the aid ofmethod steps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claimed invention.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of certainsignificant functions. The boundaries of these functional buildingblocks have been arbitrarily defined for convenience of description.Alternate boundaries could be defined as long as the certain significantfunctions are appropriately performed. Similarly, flow diagram blocksmay also have been arbitrarily defined herein to illustrate certainsignificant functionality. To the extent used, the flow diagram blockboundaries and sequence could have been defined otherwise and stillperform the certain significant functionality. Such alternatedefinitions of both functional building blocks and flow diagram blocksand sequences are thus within the scope and spirit of the claimedinvention. One of average skill in the art will also recognize that thefunctional building blocks, and other illustrative blocks, modules andcomponents herein, can be implemented as illustrated or by discretecomponents, application specific integrated circuits, processorsexecuting appropriate software and the like or any combination thereof.

What is claimed is:
 1. An axial flux stator comprises: a plurality of magnetically permeable members; an alignment plate, wherein the alignment plate includes a printed circuit board; a plurality of windings associated with the plurality of magnetically permeable members, in which the plurality of windings are wrapped around respective plurality of magnetically permeable members to produce a plurality of winding assemblies; a back iron having a planar annular ring shape, wherein first ends of the plurality of winding assemblies are disposed on the back iron by physical contact and without use of mechanical fittings and wherein second ends of the plurality of winding assemblies, which are opposite from the first ends, fit into the alignment plate to align the plurality of winding assemblies; and a solid material encasing that surrounds the back iron, the alignment plate and the plurality of winding assemblies to maintain the physical contact of the back iron to the plurality of winding assemblies.
 2. The axial flux stator of claim 1, wherein the solid material encasing comprises at least one of: an injection molding; a nonmagnetic potting material; and a nonmagnetic casting material.
 3. The axial flux stator of claim 1, wherein respective magnetically permeable member of the plurality of magnetically permeable members comprises at least one of: a soft magnetic composite stator tooth; a lamination steel stack stator tooth; and a formed ferrite material stator tooth.
 4. The axial flux stator of claim 1, wherein respective winding of the plurality of windings comprises at least one of: a bobbin supporting a wire coil; and a coil of bondable wire.
 5. The axial flux stator of claim 1, wherein the back iron comprises at least one of: a plurality of laminated steel sheets; a soft magnetic composite; and a formed ferrite material.
 6. The axial flux stator of claim 1, wherein a geometric shape of each magnetically permeable member of the plurality of magnetically permeable members is a cube, cylinder or rectangular cube shape.
 7. The axial flux stator of claim 1, wherein the alignment plate has an annular ring shape.
 8. A method of manufacturing an axial flux stator, the method comprises: assembling a plurality of inductance structures, wherein an inductance structure of the plurality of inductance structures includes a winding wrapped around a magnetically permeable member; arranging the plurality of inductance structures into a desired pattern using a carrying platform; positioning a non-permeated planar back iron having a planar annular ring shape without inclusion of mechanical fittings with respect to the plurality of inductance structures to create a substantially air-gapless magnetic coupling between the non-permeated planar back iron and the plurality of inductance structures; removing the carrying platform; and encasing, using solid encasing material, the plurality of inductance structures and the non-permeated planar back iron to maintain the substantially air-gapless magnetic coupling, wherein the encasing substantially fully surrounds the plurality of inductance structures and the non-permeated planar back iron and holds the plurality of inductance structures and the non-permeated planar back iron in place, wherein the encasing has a geometric shape corresponding to the back iron and an opening of the encasing allows a rotor to at least partially reside therein and, when the axial flux stator is energized, produces an axial flux to rotate the rotor.
 9. The method of claim 8, wherein the encasing the plurality of inductance structures and the non-permeated planar back iron comprises at least one of: injection molding the plurality of inductance structures and the non-permeated planar back iron; potting, with a nonmagnetic potting material, the plurality of inductance structures and the non-permeated planar back iron; casting, with a nonmagnetic casting material, the plurality of inductance structures and the non-permeated planar back iron; and assembly the plurality of inductance structures and the non-permeated planar back iron within a pre-fabricated housing.
 10. The method of claim 8, wherein the magnetically permeable member comprises at least one of: a soft magnetic composite stator tooth; a lamination steel stack stator tooth; and a formed ferrite material stator tooth.
 11. The method of the claim 10, wherein the winding comprises at least one of: a bobbin supporting a wire coil; and a coil of bondable wire.
 12. The method of claim 8, wherein the non-permeated planar back iron comprises at least one of: a plurality of laminated steel sheets; a soft magnetic composite; and a formed ferrite material.
 13. The method of claim 8, wherein when assembling the plurality of inductance structures, the windings are wrapped around respective magnetically permeable members having a cube, cylinder or rectangular cube shape.
 14. The method of claim 8, wherein when assembling the plurality of inductance structures, the windings are wrapped around respective magnetically permeable members having respective top plates at ends opposite the back iron.
 15. The method of claim 8, wherein the carrying platform has an annular ring shape. 